This Feathered Thorn caught me out - looking smaller than most and with strongly-marked cross-lines (but poorly marked pale spots in the apex of the wings). It reminded me more of dusky Scalloped Oak than Feathered Thorn at first glance, but of course a closer inspection revealed the true identity, with the white based antennae eliminating any niggling doubts. Actually doesn't seem all that unusual going by photos online, but looked it to me at the time!